Although a variety of ball bearings and ball bearing assemblies have been devised in the past for meeting limitless situations where friction must be minimized, a constant effort is being made to improve the effectiveness of such bearing assemblies while simultaneously lowering their cost. This is of particular importance where the bearings are manufactured in large quantities for a variety of purposes, such as in caster wheels, conveyor wheels, small truck wheels and in wheels for other vehicles of generally similar nature. Where the production of such bearing assemblies is on the order of several hundred or more per hour, it is apparent that even a small reduction in the unit cost of a bearing assembly will result in greater savings, both to the manufacturer of the bearing assemblies and to the users thereof. On the other hand, in view of the critical part played by such bearing assemblies in practically all of their usual locations of use, it is equally apparent that such cost reductions, if any, must be made without sacrificing quality.
Bearings and the wheels associated therewith of this general nature have long been known and one such bearing is shown and described in U.S. Pat. No. 3,807,817, assigned to the same assignee as is the present invention. However, in a continuing effort to improve the quality of the product while at the same time reducing its cost, a great deal of effort has been made to detect points in the previous devices at which such improvements and/or cost reductions can be made. Thus, in such wheels and their bearing assemblies as shown in said patent, as well as in other generally similar patents, such as U.S. Pat. Nos. 4,072,373 and 4,122,580, both of which are assigned to the same assignee as is the present invention, there are shown axles for the support of the bearings which in turn support the wheels, which bearings are locked in position by the structure of the axle. This general feature has proven to be very durable in the field. However, it is important that the dimensional relationships between the axially spaced bearing races be maintained within prescribed limits. If the structure which holds the inner bearing race in fixed relationship to the axle is not carefully controlled, the wheel will be permitted to shift axially relative to the axle within the axial tolerance space provided between the inner bearing race and the outer bearing race. Heretofore, the bearings have provided a predesignated axial tolerance space so that there would exist a minimal amount of relative axial shifting movement between the axial and the wheel. It is accordingly desirable to eliminate the relative axial shifting movement between the axial and the wheel but such would not be possible without subjecting the bearing balls and bearing races to adversely high stress loads which could, in the long run, reduce the effective life of the bearings. It is desirable, therefore, to provide an effective means for limiting this relative axial movement while simultaneously further enhancing the life expectancy of the bearing construction.
Accordingly, the objects of the invention include:
1. To provide a bearing and wheel construction adaptable for use under high production conditions which will produce a very inexpensive wheel and yet one which will be solid, firm and capable of long and accurate operation.
2. To provide a bearing and wheel construction, as aforesaid, which will eliminate some of the manufacturing steps now required in certain present constructions of this type but will do so without sacrifice in quality of the resultant product.
3. To provide a bearing and wheel construction, as aforesaid, which will have other advantages and economies recognized by persons skilled in the art but which will at the same time provide a bearing capable of withstanding substantial abuse and requiring only minimal maintenance, such as is recognized as required for a variety of commercial applications, such as use in shopping carts.
4. To provide a bearing and wheel construction, as aforesaid, wherein the axial tolerance space between the inner and outer bearing races of each bearing construction is initially less than the diameter of the bearing balls that are to be inserted therebetween but providing elastically flexible structure for holding one of the bearing races in a position to define the preassembled axial tolerance space so that after the bearing balls are inserted between the bearing races, the resulting structure will cause an elastic urging of the bearing races into engagement with the bearing balls so that shock loads applied to the wheel will not be applied directly to the bearings but will be absorbed by the elasticity of the material engaging one of the bearing races.